1. Field of the Invention
The present invention relates to an inclination adjusting apparatus used for adjusting the inclination of a ferrule held at a predetermined position in front of an objective lens when analyzing the form or the like of a leading end part of the ferrule accommodated within an optical connector plug by using a microscopic interferometer apparatus (also known as “interferometric microscope apparatus”), for example; and a microscopic interferometer apparatus equipped with this kind of inclination adjusting apparatus.
The present invention also relates to a ferrule clamping apparatus for holding a ferrule at a predetermined position in front of an objective lens when analyzing the form or the like of a leading end part of the ferrule accommodated within an optical connector plug by using a microscopic interferometer apparatus; and a microscopic interferometer apparatus equipped with this clamping apparatus.
2. Description of the Prior Art
Research and development of optical fibers used for optical communications have recently been well underway. Known as an example of this kind of optical fibers is one comprising a core having an outer diameter of about 10 μm; and cladding layer, disposed at the outer periphery of the core, having an outer diameter of about 125 μm; whereas the optical fiber is further equipped with a ferrule, disposed at a connecting end part thereof, for connecting the optical fiber to anoher optical fiber.
The ferrule is a cylindrical component constituting an optical connector for holding and securing one end of the optical fiber in order to connect the optical fiber to another optical fiber. After an optical fiber is inserted and secured with an adhesive or the like to the center part of the outer diameter of a ferrule, the leading end of the ferrule is polished into a mirror surface, so that two optical fibers held by respective ferrules can be connected to each other when the leading end faces of the two ferrules are butted against each other.
While the leading end face of the ferrule has been known to be polished into a plane orthogonal to the optical axis or a plane obliquely intersecting the optical axis, attention has recently been directed to one whose leading end face is subjected to PC (physical contact) polishing so as to attain a convex spherical form such that the leading end face is elastically deformed by a pressure for butting the leading end faces of ferrules against each other.
For reducing the optical loss occurring when optical fibers are connected to each other, various high-precision specs have been defined by JIS. For the PC-polished ferrule, six μm-order specs such as dimensional errors in the radius of curvature of the leading end face and positional deviation errors between the apex of the spherical leading end face of the ferrule and the center of the core of the optical fiber (the center of the fiber outer form) have been defined.
There are cases where microscopic interferometer apparatus are used for inspecting whether produced ferrules conform to the specs or not. A microscopic interferometer apparatus has been configured such that object light carrying phase information such as the surface form and refractive index distribution of a minute sample and reference light are caused to interfere with each other, thus obtained interference fringes are observed, and forms and changes of the interference fringes are measured and analyzed, so as to attain the phase information of the sample.
When inspecting a produced ferrule by using such a microscopic interferometer apparatus, an inclination adjusting apparatus for adjusting the relative inclination between the optical axis of the microscopic interferometer apparatus and the optical axis of the ferrule is necessary.
Conventionally known as such an inclination adjusting apparatus is one comprising two base members opposing each other so as to be inclinable with respect to each other while using their supporting part as a fulcrum, and an adjustment screw having a leading end face formed into a convex spherical surface. The adjustment screw is rotatably threaded into and held by one of the base members while the leading end face projects toward the other base member. While the leading end face is in slidable contact with the bearing surface on the other base member side, the adjustment surface is rotated so as to change the length of projection, thereby adjusting the relative inclination between the two base members.
However, the following problem may exist in such a conventional inclination adjusting apparatus since the leading end face of the adjustment screw is formed into a convex spherical surface. Namely, when the center of the convex spherical surface at the adjustment screw leading end deviates from the axis of the adjustment screw, the diametric center of the convex spherical surface rotates about the adjustment screw axis as the adjustment screw rotates. When the bearing surface on the other base member side coming into contact with such an eccentric convex spherical surface is formed into a groove having a V-shaped cross section, it restricts the sliding of the convex spherical surface to only a predetermined direction (in which the groove extends). Therefore, when the adjustment screw is rotated, a force may act to press the bearing surface to a direction substantially orthogonal to the predetermined direction. Such a force may cause the two base members to shift relative to each other, thereby adversely affecting the inclination adjustment.
The amount of eccentricity of the convex spherical surface at the adjustment screw leading end is usually so small that the amount of relative positional deviation between two base members mentioned above seems to be kept small. When the form of the ferrule is measured by using the above-mentioned microscopic interferometer apparatus, however, even a minute positional deviation occurring when adjusting the inclination of the ferrule may greatly affect the measurement, since it is necessary for the ferrule leading end part to be held with a high accuracy at a predetermined position in front of the objective lens of the microscopic interferometer apparatus.
On the other hand, when inspecting a produced ferrule by using such a microscopic interferometer apparatus, a clamping apparatus is necessary for holding the ferrule to be inspected at a predetermined position in front of the objective lens of the microscopic interferometer apparatus with a high positional accuracy. Since the ferrule is usually accommodated within a tubular member constituting an optical connector plug, the ferrule clamping apparatus is adapted to clamp the ferrule in a state accommodated within such a tubular member.
FIG. 13 shows a conventional example of such a ferrule clamping apparatus. FIG. 13 is a sectional view of a conventional clamping apparatus in a state holding a ferrule. The ferrule 420 shown in FIG. 13 holds and secures an end part of an optical fiber, which is not depicted, while being accommodated within a tubular member constituting an optical connector plug 400. The clamping apparatus 500 comprises a support 510 for supporting the ferrule 420 from one side thereof, a shifter 520 disposed so as to be displaceable with respect to the support 510, and a pressing member 530 for pressing the shifter 520 so as to displace the latter.
The shifter 520 opposes the support 510 across the ferrule 420, while being displaceable between a clamp position in contact with the other side of the ferrule 420 and a clamp release position separated from this side. The pressing member 530 comprises a screw shaft 531 engaging a screw hole 511 formed in the support 510, and a lever member 532 for rotating the screw shaft 531 about its axis C; and is configured so as to suppress the shifter 520 downward while in a state where a spherical leading end face of the screw shaft 531 is in contact with the upper face of the shifter 520.
In the clamping apparatus 500, the shifter 520 pressed by the pressing member 530 is displaced from the clamp release position to the clamp position, so as to abut against the other side of the ferrule 420, whereby the ferrule 420 can be held by the support 510 and the shifter 520.
The conventional clamping apparatus 500 shown in FIG. 13 may be problematic as follows. Namely, though the leading end part of the ferrule 420 accommodated within the tubular member 410 projects from the leading end of the tubular member 410, the length of projection is often very short. Though the support 510 and shifter 520 are partly extended into the tubular member 410 in order to secure a chuck margin for the ferrule 420, the line of action (coinciding with the axis C) of a force passing the pressing point P of the pressing member 530 is located on the outside of the leading end of the tubular member 410. Therefore, the position of line of action of the force may deviate from the area of ferrule 420 (area between points S and T in FIG. 13) supported by the support 510. When the pressing member 530 presses the shifter 520 in such a state, the shifter 520 may be twisted (in the direction rotating the shifter 520 clockwise in FIG. 13), which makes it difficult to hold the ferrule 420 stably or in a predetermined posture with a high accuracy.
When the ferrule is held unstably in a ferrule clamping apparatus used in a microscopic interferometer apparatus, the ferrule may shift its position during observation, thereby adversely affecting the measurement and analysis. When the ferrule is not held in a predetermined posture, highly accurate measurement and analysis cannot be carried out, either.